PsychoPy is an open-source software package for designing and running psychology, neuroscience, and psychophysics experiments. It allows researchers to create experiments using a graphical builder interface (no coding required) or through Python scripting for more flexibility. PsychoPy supports presenting stimuli (visual, auditory, or text), collecting responses (e.g., keyboard, mouse, eye-tracking, EEG triggers), and running experiments both in the lab and online via Pavlovia. It’s widely used in cognitive science and behavioral research due to its accessibility, flexibility, and strong community support.